The present invention relates to a zip-fastener, and more specifically to the fixation of interlocking Plastic teeth on zipper tapes.
A regular zip-fastener is generally comprised of two zipper tapes, two rows of interlocking metal or plastic teeth fastened to the zipper tapes, and a sliding device pulled to close/separate the two rows of interlocking plastic teeth. In a zip-fastener with interlocking plastic teeth, the teeth which are directly molded on the zipper tapes tend to be pulled away from the respective zipper tapes when the sliding device is pulled to close/separate the teeth (see FIGS. 1 and 2). There is known another structure of zip-fastener in which the interlocking plastic teeth are separately molded from nylon and then stitched to the zipper tapes (see FIG. 3). During fabrication, interlocking plastic teeth are disposed in an extended out condition, then arranged in a row on a zipper tape, then stitches are sewn on the zipper tape to fix the teeth to the zipper tape, and then the folded up zipper tape is fix in shape by stitches. Because the interlocking plastic teeth are separately made and then fastened to the respective zipper tapes by a special sewing machine, the fabrication procedure of this structure of zip-fastener is complicated. When the extended out teeth are folded up with the respective zipper tape, the two symmetrical halves of each tooth must be accurately aligned. If the two symmetrical halves of one tooth are not accurately aligned, the finished zipper fastener becomes useless. Furthermore, when the sliding device is suddenly pulled to close/separate the interlocking plastic teeth, the teeth tend to be forced out of position.
The present invention has been accomplished to provide a zip-fastener which eliminates the aforesaid drawbacks. According to one aspect of the present invention, the hollow lower face of each of the interlocking plastic teeth, which are directly molded on the zipper tapes, has two recessed retaining portions at two opposite vertical lateral sides, and top and bottom transverse thread grooves disposed at top and bottom sides and respectively connected between the recessed retaining portions, and stitches are sewn on zipper tapes around the recessed retaining portions and transverse thread grooves of each tooth to fixedly secure the teeth to the zipper tapes. According to another aspect of the present invention, the color of the threads for the stitches can be determined subject to the color of the zipper tapes used, so as to make a prominent contrast.